The continuing need for energy conservation has produced renewed interest in the diesel engine as an alternative to the spark-fired piston engine. In addition, it has created a need for greater fuel economy in such engines and an attendant need for improved timing apparatus and diagnostic equipment which is both inexpensive and easy to use. Conventional timing apparatus employs the use of timing marks on a flywheel located at the bottom of the engine. Due to the location of the engine flywheel, however, it has been difficult in many instances to read the actual ignition advance from the flywheel or provide any degree of resolution for readings between calibrated markings on the flywheel. In diesel engines graduated flywheel markings are not provided by many manufacturers due to the lack of any convenient way to detect the time of fuel injection, the time of cylinder firing or other parameters or events occurring during the combustion cycle of a given diesel cylinder.
With the advent of suitable transducers for detecting fuel injection or firing in a given cylinder, the need for and desirability of adequate timing apparatus has been further enhanced. Fuel injection and cylinder transducers of the type described are disclosed in the U.S. Pat. No. 4,036,050 of Dooley and Yelke dated July 19, 1977 and in the copending application of Dooley and Yelke Ser. No. 796,008 now U.S. Pat. No. 4,109,518. However, available fuel line transducers produce output signals which, in addition to the primary output pulses created at the initiation of injection, include ringing and spurious variations resulting from secondary effects of the fuel surge and engine vibrations.